This invention relates to a FAIMS (Field Asymmetric Ion Mobility Spectrometry) spectrometer chamber, a device intended to detect chemical contamination.
Modern spectrometer scanners detect and identify most organic substances regarded as highly toxic. Currently, the detection of highly toxic chemicals (chemical weapons and toxic industrial materials) is performed by detectors based on IMS technology (ion mobility spectrometry). These are typically classical spectrometers operating at a temperature of about 50° C., with high sensitivity, but not very high resolution, which in practice leads to false alarms. The indicator, after detecting chemical contamination, generates a warning signal, i.e. it activates a beep and light or sends a signal to activate user-defined devices, such as ventilation devices or alarm systems. The number of false alarms should be as low as possible, as this undermines confidence in the contamination detection system and may cause the unnecessary implementation of emergency procedures.
The IMS detector chamber is divided into two areas. The first is the area from the semi-permeable membrane to the injection grid, in which ionization takes place by a β- or α-radioactive source, the second is the drift area—from the injection grid to the collecting electrode. A high voltage (generally 1.5 kV to 3 kV) is applied to the grid in front of the radioactive source, while the metal rings from the source to the collecting electrode have ever lower potentials. The field is thus shaped so that the ions from the ionization area move in straight lines to the collecting electrode. Most gaseous substances have different rates of mobility, so the transit time of the ions through the drift area varies, allowing for their identification.
Currently there is much research being carried out into the improvement of the properties of devices used to detect contamination. One solution is the coupling of the classical ion mobility spectrometer with a spectrometer with a high intensity, high frequency transverse field—FAIMS in a cascade sequence. FAIMS technology is based on the phenomenon of the segregation of ions passing through the detector. The FAIMS detector is constructed of ceramic plates opposite each other to which high voltage is applied at high frequencies. Under the influence of the electric field created within the detector segregation takes place at the collecting electrode. The observed segregation of ions in the gas flowing through results from their varying mobility in fields of greater and lesser intensity. The mobility of the ions is dependent on mass, the charge of the ion and the velocity of the gas flow. Under the influence of an alternating electric field applied to the electrodes, ions whose mobility does not fulfill the conditions of stable flow through the detector are captured. Considering the dependence of the mobility of the ions from the particles migrating through the active interior of the spectrometer on the value of the compensated field, we are dealing with a type of ion filter. The structure of the hybrid FAIMS-1MS system is based on using the FAIMS spectrometer as the first step, but without the collecting electrode. It works on a principle similar to an ion trap. After passing through the ionization source, ions of the analyzed gas pass in to the ion trap, formed of two rectangular plates parallel to one another. Between the covers a high intensity field of over 10,000 [V/m] is applied. Thanks to the fact that the mobility of the ions is dependent on the electric field, ion separation can be achieved, since the electric field in the ion trap can be shaped such that only selected ions reach the collecting electrode.
FAIMS spectrometers are approximately 10 times as sensitive, furthermore, they permit the separation of gaseous substances such as acetone, benzene and toluene, which to date have not been differentiated by classical IMS spectrometers, even those with high resolution.
An important factor in the operating of FAIMS spectrometers, omitted in scientific reports or patent descriptions, is the temperature stability of the gas flow. The temperature of the gas has a significant effect on the mobility of the ions, thus it has an effect on the location of the electrical peaks arising from different gaseous substances.
The construction of such closed chambers in glass systems is known, allowing for high purity in the chamber, but unfortunately such systems do not ensure the appropriate temperature stability of the gas flow.
The aim of the invention was to develop a chamber in which the drawbacks of current devices have been eliminated.